關鍵詞：資訊隱藏、小波轉換、適應性

資訊嵌入的技術是讓我們能夠在多媒體檔案上嵌入額外資訊，以達到秘密通訊的效果。一段而言資訊嵌入可以分為兩大類的應用，第一類是用來保護媒介的，也就是數位浮水印，第二類就是利用媒介來保護藏入的資訊，也就是隱像學。在這篇論文中，我們所強調的是隱像學的部分，我們希望在人眼辨視力的極限下，藏入最大量的資料，以達到我們的要求。
近年來，在資料隱藏的技術上，通常是利用修改一些在原始影像中較不重要的資訊以達到藏入的效果。目前最主要的研究領可以分為兩類，第一類是在空間域下對影像做修改。在空間域中最常用的方式修改像素資料的LSB以減少對圖像的影響。第二則是將圖像從空間域中轉至頻率域，再針對高頻的部分做修改。
在此篇論文中，我們提出了基於整數小波轉換的適應性資料隱藏的方式。我們將原始的影像切割成8x8的區塊。在經過小波轉換後，我們可以得到四個子頻段，分別為LL, HL, LH及HH。完成這個部分後，就可以利用我們所提出的函數去判斷在HL, LH及HH 這三個子頻段中每一個小波係數所能藏入的資料長度。並且我們會將這個結果暫存下來，利用這個結果去針對LL子頻段加以分析，決定是否要進行二階的小波轉換，在運算次數與資訊藏量中取得平衡。我們同時與其他方法做一個比較，在實驗結果中，相同的品質中我們可以得到更大的隱藏量。而在於最差的情形下，我們提出的方法比傳統的最小位元取代法要好上很多。

Key words: data hiding, wavelet transform, adaptive
In this paper, we propose an adaptive data hiding method in the frequency domain. We divide original image into 8*8 sub-blocks and use Haar Discrete Wavelet Transform (HDWT) to decompose each block to obtain sub-bands, LL, HL, LH and HH. A data hiding capacity function is proposed to analyzes each band except LL. It can be used to judge the hiding length of each coefficient of each band and to decide whether the subbands LH, HL and HH are complex or not. If these three sub bands are complex, the LL band is further decomposed and more data bits and be embedded. We compare our method with other method. From the experiments, we find that the proposed method has a larger data hiding capacity than that of other method.

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